The following year, [1]} presented the client-server and peer-to-peer architectures for the HFL scenario. In the client-server architecture, the server receives all model updates from participants (encrypted or in plain text, depending on the scenario) and aggregates them. The peer-to-peer architecture is interesting because it eliminates the need for a central coordinating point and its associated attack surface. In this approach, participants aggregating the models can be randomly selected or follow a predefined chain.
